Only a few researchers have studied the effect of carbon fiber repair on corrosion processes. The main protective effect is the "protective barrier" which is sometimes called passive protection against corrosion, comparable to some techniques such as anticorrosion coatings of concrete structures. Indeed, CFRP materials, applied as external reinforcing material on reinforced concrete structures form a protective barrier against the penetration of moisture and pollutants such as chlorides or carbon dioxide.188.8.131.52.5 Apart from this impermeable barrier action, it has been found in these studies that the confinement of CFRP concrete has a positive influence on the onset of corrosion and on its velocity. Very little research has investigated the coupling between mechanical reinforcement and impressed current system.6,7,8
Approximately one cubic yard of concrete is placed annually per person on the planet with existing concrete estimated to be 30 times this amount (1). This presentation will discuss the basics of concrete, the various alternatives for control of corrosion in reinforced concrete structures, including prevention, protection, and mitigation, and strategies for selection of these alternatives. The pros and cons of each technique will be reviewed as well as the applicability considerations for the life cycle of the structure.
Corrosion of steel in reinforced concrete bridges is a major concern for the structural integrity, long-term durability, and maintenance of the highway infrastructure. Statistics from a national study in 2002 indicated that approximately 15% of the national bridge inventory is structurally deficient because of corrosion and the national annual direct cost exceeded $8 billion.1 In the state of Florida, the typical design life expectation for the >6,000 bridges in the state highway infrastructure exceed 75 years.
Marine environments can be very aggressive and present significant challenges in maintaining key infrastructure from the effects of corrosion. In Florida, thousands of bridges are in coastal areas and are continually, or periodically exposed to saltwater conditions. A clear majority of these bridges were constructed using steel reinforced concrete and are supported by precast pilings situated in saltwater, so for this reason, cathodic protection is a necessary strategy for controlling the effects of saltwater induced corrosion.
Toward the early 1980s, the Florida Department of Transportation (FDOT) began the evaluation of different approaches to control saltwater induced corrosion. Some of these included the use of integral pile jackets, specialty materials for concrete repairs, surface applied coatings and other innovative approaches utilizing galvanic anode technology. One such system was jointly developed with industry partners and sponsored by the Federal Highway Administration (FHWA) using integral pile jackets lined with expanded zinc mesh anodes to apply cathodic protection. This innovative approach provides for the problem of concrete repair while at the same time stopping the on-going process of corrosion both combined in one application. Both laboratory and field trials validated the benefits to this approach and confirmed that the system can mitigate corrosion and extend the useful service life of pilings by more than 20 years.
Impressed current cathodic protection (ICCP) is one corrosion management approach adopted by the Port of Newcastle (PoN) for their reinforced concrete wharves. The Port’s West Basin 3 wharf, has ICCP systems installed to select substructure concrete elements (beams). The West Basin 3 ICCP system to the front beam soffit section was installed in 1998 (rear beam soffit sections having been protected from 2014). Other ICCP systems have also been installed by the PoN during the period 2002 to 2005 for the West Basin Wharf 4, East Basin (1 & 2) wharves and the Kooragang K2 wharf. This paper provides background to the different ICCP systems utilized and details performance results for the West Basin 3 front beam ICCP system dating back more than 20 years. Monitoring results are presented and discussed. Performance assessment to protection criteria is undertaken and the CP system maintenance requirements are summarized.
Managing aging reinforced concrete infrastructure is a complex and capital-intensive task, particularly in harsh marine and coastal environments. Corrosion from saltwater, coupled with wet and dry cycles, are particularly problematic for long-term durability of reinforced concrete. The Gulf Coast presents a challenge for maintaining service life of concrete structures that are exposed to high levels of chlorides, either by direct contact with salty or brackish water or by indirect contact with salt spray. Chlorides induce corrosion of the steel reinforcement which initiates cracking and spalling of the concrete, reducing the service life of the structure.
Steel rebars in concrete structures are usually protected from corrosion by a thin layer of passive film, which is formed due to the high alkalinity of concrete pore solution.1-2 However, this protective passive film could be damaged by penetration of chloride into concrete structures in marine environments or exposure to the use of de-icing salt for the removal of snow and ice in winter times.3 Penetration of chloride would impair the passive film locally and initiate pitting corrosion.